Calculation methods and insulation techniques for steel stud walls in low-rise multifamily housing

This paper examines calculation methods and insulation techniques applied to a construction project that comprises 1,200 two-story housing units built in New York City. The R-value is calculated using several methods. Two-dimensional finite-difference results for a stud-and-tracks assembly are first fine-tuned against a three-dimensional model. The two-dimensional computer program is then used to analyze the exact configuration of the steel frame construction of the entire building, accounting for all double studs, cripple studs, jambs, lintels, and beams, as well as metal ties and fasteners. The results emphasize the need for a whole-wall R-value calculation that accounts for all framing in the wall, rather than a clear-wall approximation. The error of the clear-wall calculation is in the 40% to 50% range for this type of house. Thermally improved wall constructions are examined. For the same center-of-cavity R-value, a wall with insulating sheathing has a total R-value that is 13% higher than one without insulating sheathing. The risk of moisture condensation is significantly reduced with the improvements.